The high load design was adopted to reduce blades to increase diameter of disc while reducing the circumferential leakage area. And aft-loaded cascades were employed to retrofit design to minimize the secondary flow loss brought about by high load design. For the fixed geometry turbine

only the flow field of the variable geometry turbine of driving axis and disc type crown variable geometry turbine was numerically calculated. Three kinds of turbine performance under all conditions were analyzed. Result shows that

under the big clearance

intensity of the clearance leakage vortex was big. If merged with the passage vortex

the leakage loss became bigger. The high load design brought the secondary flow loss. The method reduced the circumferential leakage area

restraining greatly the merges between the leakage flow and the secondary flow to reduce the clearance leakage loss. High load design can effectively restrain the development trend of passage vortex

thereby reducing the secondary flow loss. With two measures

the variable geometry turbine has high performance under overall conditions.